Conventionally, a battery charger used for charging a batter pack has been desired, in order to meet increased capacity of a secondary battery in the battery pack, to increase a charging current to ensure charging capacity and shorten charging time. However, increasing the charging current causes a large current to flow into a charging circuit in the battery charger and the secondary battery in the battery pack. This causes an extreme increase in temperature of the charging circuit and the secondary battery. As a result, degradation and malfunction of the secondary battery and components constituting the charging circuit may occur.
To solve the above-described problem, there is conventionally known a battery charger provided with an air intake fan that generates airflow for cooling a charging circuit therein and a secondary battery in a battery pack while the battery pack is being charged.